This invention relates to a dragline bucket, viz., a bucket having drag, hoist and dump lines connected thereto and, more particularly, to a bucket having a uniquely located center of gravity which develops heretofore unobtainable advantages in operation.
Although dragline buckets have been used for many years, and many designs employed, no one has focused on the importance of proper location of the center of gravity of the bucket. The only U.S. patent uncovered which mentions center of gravity is Berner U.S. Pat. No. 2,168,643--but this only in connection with the location of a special latch for the hoist line (page 3, line 10).
I have discovered certain relationships in dragline bucket construction that avoid the disadvantages of the prior art buckets. One significant drawback of prior art buckets is that when they began to tip, it took less and less pulling force to continue the tipping action. This meant that when tipping started, the operator had to relax the drag force and re-start the cut. Another drawback was that the prior art designs maximized the dragline force only at the end of a cut, i.e., when the bucket was tilted upwardly. Although this was beneficial at that particular part of the cut, it meant that less than maximum force was applied during the major portion of the cut. The invention not only overcomes these drawbacks but provides other advantages as well.
According to the invention, especially advantageous performance is attained where the bucket has a center of gravity located in relation to certain always-present portions of the bucket, viz., the hitch pivot axis, the tooth tip, and the bucket heel. More particularly, the center of gravity is located along a line making an angle of at least 90.degree. with a line from the tooth tip to the horizontal pivot axis, along a line making an angle of from about 25.degree. to about 30.degree. with a line from the tooth tip to the heel, and so located that from about 50% to about 60% of the bucket weight is on the heel in a static or non-working condition.
Another advantageous feature of the invention is a movable hitch for the drag lines. Locatable hitches have been tried for many years--see U.S. Pat. Nos. 963,561, 1,050,838, 1,951,909, 2,286,765 and 2,525,528--but none have worked out, there being no bucket commercially available for at least the last 30 years which was equipped with a movable hitch. The novel construction of the inventive movable hitch makes it useful, not only in conjunction with the above-described inventive bucket, but other buckets as well.